A cable fault can be caused by an insulation breakdown. The failure modes of such a cable fault can include a short circuit to ground and/or a “soft fault” with a relatively low electrical impedance (or resistance), comparing to that of the cable insulation, between the cable and the earth ground.
For example, in the case of the airfield lighting system, where each lighting segment may contain an array of 250 runway light assemblies coupled in series by a power cable buried in the runway which runs as much as 15 Kilometers, a power cable fault can lead to a large number of runway lights to go off, resulting in safety hazard and potentially part of the airport runways being shutdown. Sometimes, even if a power cable problem, such as the insulation deterioration, can be detected at its early stage through leakage current tests, no further, action can be taken due to lack of problem location information, until the problem gets further escalated to cause an actual damage.
As can be seen, there is a need for an effective cable problem detection method, and particularly a way to obtain the knowledge of the problem location, which not only can significantly shorten the time for cable maintenance, but also may effectively avoid actual damages as results of the cable fault by fixing the cable problem at its early stage.